Sketched drawings can provide solid foundations for completed drawings and may even be used by themselves as stylized finished products. Since sketches can be completed in a relatively short time while providing a broad view of the most important visual elements, sketches are a valuable planning tool for artists, animators, modelers, engineers, draftsmen, and other professions that may produce paintings, figures, flowcharts, models, and other drawings and diagrams. Moreover, since sketching is a process that almost everyone is comfortable and familiar with, sketching may be advantageously employed by people at all artistic skill levels.
However, to transition from an initial rough sketch to an intermediate or finished drawing, it is essential to segment portions of the sketch into specific regions or layers. Once separated into layers, many tasks towards the completion of the drawing are readily solved or greatly assisted, including object occlusion, moving and deforming of parts, animation inbetweening or tweening, line or path stroking with color, and area shading with colors or patterns such as textures, hatching or screen tone. Conventionally, such layer segmentation is done manually by the user, often a time-consuming, tedious, and error-prone process, particularly for sketched drawings and for users unfamiliar with working with multiple drawing layers.